PubMed Health⌕ Search

PubMed · 11295317

Polyphenols from Eucalyptus ovata.

Abstract

From the leaves of Eucalyptus ovata 13 known compounds, four flavonol glycosides and nine tannins, including the trimer gallocatechin-(4alpha-8)-gallocatechin-(4alpha-8)-catechin (1), were isolated. The spectral data of the peracetate derivative of the trimer are reported.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S C Santos, P G Waterman. 2001. Polyphenols from Eucalyptus ovata.. https://doi.org/10.1016/s0367-326x(00)00298-7

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

CsMYB219 and CsMYB196 influence epigallocatechin gallate biosynthesis in tea plant (Camellia sinensis) by regulating CsSCPL1A gene expression.

Epigallocatechin gallate (EGCG) is the most abundant and biologically active catechin in tea leaves and has been widely utilized in the development of functional foods. EGCG is catalyzed by serine carboxypeptidase-like 1A (CsSCPL1A) acyltransferases in tea plants. Although CsSCPL family genes are regulated by several transcription factors (TFs), systematic studies on their regulation by MYB TFs are lacking. This study integrates targeted metabolomics, transcriptomics, DNA-protein, and protein-protein interaction analyses to elucidate the transcriptional regulation of EGCG biosynthesis-related genes CsSCPL4 and CsSCPL5-1 by R2R3-MYB TFs. CsMYB219 and CsMYB196 can specifically bind to CsSCPL4 and CsSCPL5-1 promoters and activate their expression. CsMYB196 also interacted with CsTT8a and CsTTG1 to activate the transcription activity of CsSCPL4 and CsSCPL5-1 promoters by forming a MYB/bHLH/WD40 (MBW) complex. Promoter truncation assays delineated MYB-responsive cis-elements in CsSCPL4 (-613 to -1 bp with enhancers at -1967 to -1622) and CsSCPL5-1 (-503 to -296 bp). Silencing of CsMYB219 and CsMYB196 by virus-induced gene silencing (VIGS) assay significantly reduced the expression levels of CsSCPL4 and CsSCPL5-1 and EGCG content in tea leaves. Transient overexpression of CsMYB219 and CsMYB196 in tea leaves upregulated CsSCPL4 and CsSCPL5-1 expression and elevated EGCG content. These findings enhance our understanding of the regulatory network underlying EGCG biosynthesis in tea plants and provide a solid foundation for future genetic improvement of tea plant cultivars.

Catechin↗

Influence of epicatechin reactions on the mechanisms of Maillard product formation in low moisture model systems.

The influence of the polyphenolic compound epicatechin on Maillard chemistry was investigated under simulated roast conditions (10% moisture at 220 degrees C for 10 min). Quantitative gas chromatography (GC) analysis indicated that the addition of epicatechin to glucose or fructose/glycine model systems significantly reduced the generation of hydroxyacetone, 2-methylpyrazine, 2,3,5-trimethylpyrazine, furfural, 2-acetylfuran, 5-methylfurfural, 2(5H)-furanone, 2-acetylpyrrole, and furfuryl alcohol. These analytes were reported to be primarily generated from intact C2, C3, C4, C5, and C6 sugar fragments based on gas chromatography/mass spectrometry quantitative isotopomeric analysis of a 1:1 13C6:12C6 hexose sugar/glycine model system. Liquid chromatography/mass spectrometry qualitative isotopomeric analysis of a 1:1 13C6:12C6 hexose sugar/glycine/epicatechin model systems confirmed epicatechin reacted with Maillard reactants in the model systems; two main reaction products were reported, epicatechin-C5 and -C6 sugar fragment adducts. In addition, LC/MS analysis of a model system consisting of only 3-deoxy-2-hexosulose and epicatechin identified 3-deoxy-2-hexosulose as a precursor of the epicatechin-C5 and -C6 sugar fragment adducts reaction products. These results imply that epicatechin quenched 3-deoxy-2-hexosulose (a key source C6 to C1 sugar fragments) and consequently inhibited Maillard product formation.

Catechin↗

Food components inhibiting recombinant human histidine decarboxylase activity.

Histidine decarboxylase (HDC) catalyzes histamine formation from histidine. Histamine is a bioactive amine acting as a neurotransmitter as well as a chemical mediator. Phenolic food components have been tested for their ability to inhibit recombinant human HDC. Epicatechin gallate (ECG) was found to be a potent inhibitor as it inhibited HDC activity in a competitive manner with Ki = 10 muM against l-histidine. Epigallocatechin gallate (EGCG) showed time-dependent inhibition which disappeared under anaerobic conditions. It is probable that time-dependent inhibition could be due to the result of autoxidation of EGCG. The initial burst observed for EGCG suggests that EGCG itself is involved in HDC inhibition as observed for ECG. Our present results have shown that the tested food components can inhibit HDC activity. This inhibition likely affects histamine biosynthesis and possibly leads to controlling the biological action induced by histamine. Therefore, those food components exhibiting HDC inhibitory activity might be potentially useful in controlling histamine-induced biological actions.

Catechin↗